Data transmission method, base station, and terminal device

ABSTRACT

This application provides a data transmission method, a base station, and a terminal device. The method includes: determining, by a base station, a target base graph in N Raptor-like low-density parity-check (LDPC) base graphs; and sending, by the base station, indication information to a terminal device, where the indication information is used to indicate the terminal device to use the target base graph to perform LDPC encoding and decoding. Based on the foregoing technical solution, the base station may determine a target base graph in a plurality of Raptor-like LDPC base graphs that may be used to perform LDPC encoding and decoding, and indicate the target base graph to the terminal device. Further, for one code rate or one code length, the base station may select different base graphs as required.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/085408, filed on May 3, 2018, which claims priority toChinese Patent Application No. 201710307430.1, filed on May 4, 2017. Thedisclosures of the aforementioned applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

This application relates to the communications field, and morespecifically, to a data transmission method, a base station, and aterminal device.

BACKGROUND

In an enhanced mobile Internet (eMBB) scenario of a 5th generation (5G)communications system, a Raptor-like low-density parity-check code(LDPC) is determined to be used for data channel a coding scheme.

A Raptor-like LDPC base graph that may be used in the 5G communicationssystem is used as an example. One Raptor-like LDPC base graph may beused to perform encoding on a to-be-encoded code block with a lengthranging from 40 bits to 8192 bits, and achieves a code rate of encodingranging from ⅕ to 8/9. However, there are some problems when such a widerange of code lengths and such a wide range of code rates are supportedby using one Raptor-like LDPC base graph. For example, the Raptor-likeLDPC base graph fails to ensure encoding performance and decodingperformance of code blocks with different lengths, and fails to ensureperformance of both high-code-rate encoding and decoding andlow-code-rate encoding and decoding.

SUMMARY

This application provides a data transmission method, a base station,and a terminal device, so that an encoded transport block can meet arequirement of an actual service.

According to a first aspect, an embodiment of this application providesa data transmission method. The method includes: determining, by a basestation, a target base graph in N Raptor-like low-density parity-checkcode LDPC base graphs, where a first base graph and a second base graphare any two of the N Raptor-like LDPC base graphs, a quantity of columnscorresponding to information bits included in the first base graph isdifferent from a quantity of columns corresponding to information bitsincluded in the second base graph, an intersection between code lengthssupported by the first base graph and the second base graph is notempty, an intersection between code rates supported by the first basegraph and the second base graph is not empty, and N is a positiveinteger greater than or equal to 2; and sending, by the base station,indication information to a terminal device, where the indicationinformation is used to indicate the terminal device to use the targetbase graph to perform LDPC encoding and decoding. Based on the foregoingtechnical solution, the base station may determine a target base graphin a plurality of Raptor-like LDPC base graphs that may be used toperform LDPC encoding and decoding, and indicate the target base graphto the terminal device. Further, for one code rate or one code blocklength, the base station may select different base graphs as required.

With reference to the first aspect, in a first possible implementationof the first aspect, the sending, by the base station, indicationinformation to a terminal device includes: determining, by the basestation in at least N MCS indexes based on a correspondence between amodulation and coding scheme MCS index and a base graph, a target MCSindex corresponding to the target base graph; and sending, by the basestation, the target MCS index to the terminal device, where the targetMCS index is the indication information. The base station may use an MCSindex in existing signaling to carry the indication information.Therefore, in the foregoing technical solution, the determined targetbase graph may be indicated to the terminal device without increasingsignaling overheads and without changing a signaling structure.

With reference to the first possible implementation of the first aspect,in a second possible implementation of the first aspect,

the correspondence between an MCS index and a base graph is indicated byusing an MCS table, where the MCS table includes the at least N MCSindexes, each of the at least N MCS indexes corresponds to one of the NRaptor-like LDPC base graphs, and each of the at least N MCS indexesfurther corresponds to at least one of a modulation order and atransport block size index. The target base graph may be correlated witha transport block size. Therefore, both the target base graph and atransport block size index corresponding to the target base graph areindicated to the terminal device by using the MCS index.

With reference to any one of the first aspect or the foregoing possibleimplementations of the first aspect, in a third possible implementationof the first aspect, the method further includes: determining, by thebase station, a target lifting factor group in at least two liftingfactor groups based on requirement information, where each of the atleast two lifting factor groups includes a plurality of lifting factors,and the requirement information includes at least one of a terminaldevice type, a throughput rate requirement, a latency requirement, aninitial-transmission code rate value, and a service type; determining,by the base station based on a length of a to-be-encoded code block, atarget lifting factor in a plurality of lifting factors included in thetarget lifting factor group; and performing, by the base station, LDPCencoding on the to-be-encoded code block based on the target liftingfactor and the target base graph. Different requirements and differenthybrid automatic repeat request (HARQ) performance are satisfied byselecting proper lifting factors.

With reference to any one of the first aspect, the first possibleimplementation of the first aspect, or the second possibleimplementation of the first aspect, in a fourth possible implementationof the first aspect, the method further includes: determining, by thebase station, a target lifting factor group in at least two liftingfactor groups based on requirement information, where each of the atleast two lifting factor groups includes a plurality of lifting factors,and the requirement information includes at least one of a terminaldevice type, a throughput rate requirement, a latency requirement, aninitial-transmission code rate value, and a service type; determining,by the base station based on a length of a to-be-encoded code block, atarget lifting factor in a plurality of lifting factors included in thetarget lifting factor group; receiving, by the base station, a codeblock sent by the terminal device, where the code block sent by theterminal device is obtained by the terminal device by performing LDPCencoding on the to-be-encoded code block based on the target liftingfactor and the target base graph; and performing, by the base station,LDPC decoding on the received code block based on the target liftingfactor and the target base graph. Different requirements and differentHARQ performance are satisfied by selecting proper lifting factors.

With reference to any one of the first aspect or the foregoing possibleimplementations of the first aspect, in a fifth possible implementationof the first aspect, the columns of the second base graph are a subsetof the columns of the first base graph. This can reduce storage spacefor storing Raptor-like LDPC base graphs.

According to a second aspect, an embodiment of this application providesa data transmission method. The method includes: receiving, by aterminal device, indication information sent by a base station;determining, by the terminal device according to the indicationinformation, a target base graph used to perform low-densityparity-check code LDPC encoding and decoding, where the target basegraph is from N Raptor-like LDPC base graphs, a first base graph and asecond base graph are any two of the N Raptor-like LDPC base graphs, aquantity of columns corresponding to information bits included in thefirst base graph is different from a quantity of columns correspondingto information bits included in the second base graph, an intersectionbetween code lengths supported by the first base graph and the secondbase graph is not empty, an intersection between code rates supported bythe first base graph and the second base graph is not empty, and N is apositive integer greater than or equal to 2.

With reference to the second aspect, in a first possible implementationof the second aspect, the receiving, by a terminal device, indicationinformation sent by a base station includes: receiving, by the terminaldevice, a target modulation and coding scheme MCS index sent by the basestation, where the target MCS index is the indication information; andthe determining, by the terminal device according to the indicationinformation, a target base graph used to perform LDPC encoding anddecoding includes: determining, by the terminal device based on acorrespondence between an MCS index and a base graph, a base graphcorresponding to the target MCS index as the target base graph.Therefore, in the foregoing technical solution, the target base graphmay be determined without increasing signaling overheads and withoutchanging a signaling structure.

With reference to the first possible implementation of the secondaspect, in a second possible implementation of the second aspect, thereceiving, by a terminal device, indication information sent by a basestation includes: receiving, by the terminal device, the targetmodulation and coding scheme MCS index sent by the base station, wherethe target MCS index is the indication information; and the determining,by the terminal device according to the indication information, a targetbase graph used to perform LDPC encoding and decoding includes:determining, by the terminal device based on the correspondence betweenan MCS index and a base graph, the base graph corresponding to thetarget MCS index as the target base graph. Therefore, both the targetbase graph and a transport block size index corresponding to the targetbase graph are obtained by using the MCS index.

With reference to any one of the second aspect or the foregoing possibleimplementations of the second aspect, in a third possible implementationof the second aspect, the method further includes: determining, by theterminal device, a target lifting factor group in at least two liftingfactor groups based on requirement information, where each of the atleast two lifting factor groups includes a plurality of lifting factors,and the requirement information includes at least one of a terminaldevice type, a throughput rate requirement, a latency requirement, aninitial-transmission code rate value, and a service type; determining,by the terminal device based on a code length of a to-be-encoded codeblock, a target lifting factor in a plurality of lifting factorsincluded in the target lifting factor group; and performing, by theterminal device, LDPC encoding on the to-be-encoded code block based onthe target lifting factor and the target base graph. Differentrequirements and different HARQ performance are satisfied by selectingproper lifting factors.

With reference to any one of the second aspect, the first possibleimplementation of the second aspect, or the second possibleimplementation of the second aspect, in a fourth possible implementationof the second aspect, the method further includes: determining, by theterminal device, a target lifting factor group in at least two liftingfactor groups based on requirement information, where each of the atleast two lifting factor groups includes a plurality of lifting factors,and the requirement information includes at least one of a terminaldevice type, a throughput rate requirement, a latency requirement, aninitial-transmission code rate value, and a service type; determining,by the terminal device based on a code length of a to-be-encoded codeblock, a target lifting factor in a plurality of lifting factorsincluded in the target lifting factor group; receiving, by the terminaldevice, a code block sent by the base station, where the code block sentby the base station is obtained by the base station by performing LDPCencoding on the to-be-encoded code block based on the target liftingfactor and the target base graph; and performing, by the terminalstation, LDPC decoding on the received code block based on the targetlifting factor and the target base graph. Different requirements anddifferent HARQ performance are satisfied by selecting proper liftingfactors.

With reference to any one of the second aspect or the foregoing possibleimplementations of the second aspect, in a fifth possible implementationof the second aspect, the columns of the second base graph are a subsetof the columns of the first base graph. This can reduce storage spacefor storing Raptor-like LDPC base graphs.

According to a third aspect, an embodiment of this application providesa base station. The base station includes units configured to performthe method in the first aspect or any possible implementation of thefirst aspect.

According to a fourth aspect, an embodiment of this application providesa terminal device. The terminal device includes units configured toperform the method in the second aspect or any possible implementationof the second aspect.

According to a fifth aspect, an embodiment of this application providesa base station. The base station includes a memory, a transceiver, and aprocessor. The memory stores an instruction used to implement the methodin the first aspect or any possible implementation of the first aspect,and the processor executes, in combination with the transceiver, theinstruction stored in the memory.

According to a sixth aspect, an embodiment of this application providesa terminal device. The terminal device includes a memory, a transceiver,and a processor. The memory stores an instruction used to implement themethod in the second aspect or any possible implementation of the secondaspect, and the processor executes, in combination with the transceiver,the instruction stored in the memory.

According to a seventh aspect, an embodiment of this applicationprovides a computer-readable storage medium. The computer-readablestorage medium stores an instruction, and when the instruction is run ona computer, the computer is enabled to perform the method in theforegoing aspects.

According to an eighth aspect, an embodiment of this applicationprovides a computer program product including an instruction. When thecomputer program product is run on a computer, the computer is enabledto perform the method in the foregoing aspects.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a Raptor-like LDPC matrix;

FIG. 2 is a schematic flowchart of a data transmission method accordingto an embodiment of this application;

FIG. 3 is a structural block diagram of a base station according to anembodiment of this application;

FIG. 4 is a structural block diagram of a terminal device according toan embodiment of this application;

FIG. 5 is a structural block diagram of a base station according to anembodiment of this application; and

FIG. 6 is a structural block diagram of a terminal device according toan embodiment of this application.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions of this application withreference to accompanying drawings.

It should be understood that, the technical solutions of the embodimentsof this application may be applied to various communications systems inwhich Raptor-like LDPC matrices are used to perform encoding anddecoding, for example, a 5th generation (5G) network system and a newradio (NR) system.

Wireless transmission devices described in the embodiments of thisapplication may include a terminal device and a network device.

A terminal device described in the technical solutions of theembodiments of this application may be referred to as an accessterminal, user equipment (UE), a subscriber unit, a subscriber station,a mobile station, a mobile console, a remote station, a remote terminal,a mobile device, a user terminal, a terminal, a wireless communicationsdevice, a user agent or a user apparatus, a handheld device with awireless communication function, a computing device or anotherprocessing device connected to a wireless modem, an in-vehicle device, awearable device, and a terminal device in a future 5G network. Theterminal device may communicate with one or more core networks through aradio access network (RAN), or may be connected to a distributed networkin a self-organizing manner or a grant-free manner. The terminal devicemay be alternatively connected to a wireless network in another mannerfor communication, or the terminal device may directly perform wirelesscommunication with another terminal device. This is not limited in theembodiments of this application.

A network device described in the embodiments of this application may bea nodeB, an evolved nodeB (eNB), a base station in a communicationssystem, a base station or a network device in a future communicationssystem, and the like.

A data link layer sends data by transport blocks (TB) to a physicallayer for processing. After receiving a transport block, the physicallayer first adds cyclic redundancy check (CRC) parity bits to thetransport block, to enhance a capability of performing error detectionon the TB. An input length supported by an encoder is limited. In somecases, a length of a TB to which CRC parity bits are added may begreater than an input length supported by the encoder. In the cases,code block segmentation needs to be performed on the TB to which the CRCparity bits are added. Code block segmentation is to segment a transportblock with CRC parity bits into a plurality of code blocks (CB) whoselengths match an input length supported by the encoder, for encoding bythe encoder. In some cases, a length of a TB with CRC parity bits may besmaller than a length supported by the encoder, and in this case, fillerbits may be inserted into the TB to reach a length matching the inputlength supported by the coder.

A to-be-encoded code block described in the embodiments of thisapplication is a code block that is input into a encoder. For example,in an encoding process, CRC parity bits may be attached to a CB obtainedthrough code block segmentation, and the CB with the CRC parity bits isinput into the encoder. In the embodiments, a CB with CRC parity bits isa to-be-encoded code block or a to-be-LDPC encoded code block describedin the embodiments of this application.

FIG. 1 is a schematic diagram of a Raptor-like LDPC matrix. TheRaptor-like LDPC matrix may be divided into five parts. A, B, C, D, andE shown in FIG. 1 represent the five parts of the Raptor-like LDPCmatrix. The matrix A may be referred to as a Raptor-like LDPC base graphand corresponds to an information bit part of a coded block. The matrixB includes at least one column whose column weight is 3, and there is abi-diagonal structure on a right side of the column whose column weightis 3. The matrix C is an all-zero matrix. The matrix E is an identitydiagonal matrix. A form of the matrix D is not limited.

FIG. 2 is a schematic flowchart of a data transmission method accordingto an embodiment of this application.

201. A base station determines a target base graph in N Raptor-like LDPCbase graphs, where N is a positive integer greater than or equal to 2. Afirst base graph and a second base graph are any two of the NRaptor-like LDPC base graphs. A quantity of columns corresponding toinformation bits included in the first base graph is different from aquantity of columns corresponding to information bits included in thesecond base graph. An intersection between code lengths supported by thefirst base graph and the second base graph is not empty, and anintersection between code rates supported by the first base graph andthe second base graph is not empty.

The base station may determine the target base graph based on a currentservice requirement, for example, whether a latency or performance ispreferentially considered. For example, in a selection implementation inwhich performance is preferentially considered, optimal decodingperformance during initial transmission may be preferentially ensured.In this case, the base station prerecords matrices, in matricesprestored by a encoder, achieving optimal performance and correspondingto different input code lengths and different initial transmission coderates. The base station may select an optimal Raptor-like LDPC basegraph as the target base graph based on an actual code length and anactual code rate. In another matrix selection implementation in which alatency is preferentially considered, the base station may select amatrix based on a requirement of an actual service for a latency. Whenthe service requires a relatively low latency, the base station maydetermine to use a Raptor-like LDPC base graph in which a quantity ofcolumns corresponding to information bits is relatively small as thetarget base graph.

Certainly, the base station may alternatively determine the target basegraph based on another selection condition. For example, the basestation may alternatively determine the target base graph based on acurrent service type, such as enhanced mobile Internet (eMBB) andultra-reliable and low latency communications (uRLLC).

Optionally, in some embodiments, the columns of the second base graphare a subset of the columns of the first base graph.

More specifically, in some embodiments, it is assumed that the firstbase graph includes K columns. The second base graph may include K′columns, where K′ is a positive integer smaller than K. The first columnto the k^(th) column in the K′ columns are the first column to thek^(th) column in the K columns, and the (k+1)^(th) column to the K′^(th)column in the K′ columns are the (K−(K′−k−1))^(th) column to the K^(th)column in the K columns, where K, K′, and k are all positive integers,K′ is smaller than K, and k is smaller than K′.

Optionally, in some embodiments, k is a positive integer greater than 1.For example, the first base graph includes 32 columns, and the secondbase graph includes 16 columns. The 1^(st) column to the 10^(th) columnin the second base graph may be the 1^(st) column to the 10^(th) columnin the first base graph. The 11^(th) column to the 16^(th) column in thesecond base graph are the 27^(th) column to the 32^(nd) column in thefirst base graph.

Further, in some embodiments, k may be equal to K′−1. For example, thefirst base graph includes 32 columns, and the second base graph includes16 columns. The 1^(st) column to the 15^(th) column in the second basegraph may be the 1^(st) column to the 15^(th) column in the first basegraph. The 16^(th) column in the second base graph is the 32^(nd) columnin the first base graph.

202. The base station sends indication information to a terminal device,where the indication information is used to indicate the terminal deviceto use the target base graph to perform LDPC encoding and decoding.

203. The terminal device determines the target base graph according tothe indication information.

Optionally, in some embodiments, the base station may determine, in atleast N MCS indexes based on a correspondence between a modulation andcoding scheme (MCS) index and a base graph, a target MCS indexcorresponding to the target base graph. The base station may send thetarget MCS index to the terminal device. The target MCS index is theindication information.

The correspondence between an MCS index and a base graph may beindicated by using an MCS table. The MCS table includes the at least NMCS indexes, and each of the at least N MCS indexes corresponds to oneof the N Raptor-like LDPC base graphs. Each of the at least N MCSindexes further corresponds to at least one of a modulation order and atransport block size index.

Different target base graphs used to perform LDPC encoding usuallysupport different code rate ranges and different code length ranges. Forexample, a larger Raptor-like LDPC base graph is usually suitable forsupporting a longer code length and a higher code rate, and a smallerRaptor-like LDPC base graph is usually suitable for supporting only ashorter code length and a lower code rate. For a code length and a coderate that are supported by a matrix alone, when an MCS index is used todetermine a transport block size and a modulation order that correspondto the MCS index, the code length and code rate are determined, todetermine information about a target base graph. For a code lengthsupported by a plurality of matrices and a code rate supported by aplurality of matrices, based on different selection policies, both atarget base graph and a transport block size index corresponding to thetarget base graph may be indicated to the terminal device by using anMCS index.

After determining the target base graph, the base station may determine,based on the target base graph, an MCS index corresponding to the targetbase graph based on the target base graph. Specifically, the basestation may receive channel environment information sent by the terminaldevice, for example, a channel quality indicator (CQI). The base stationmay determine a plurality of candidate MCS indexes based on the CQI.Modulation orders and transport block size indexes indicated by thesecandidate MCS indexes all correspond to the CQI. In addition, basegraphs indicated by these candidate MCS indexes are different. The basestation may determine, in the candidate MCS indexes based on thedetermined target base graph, the MCS index indicating the target basegraph, and send the determined MCS index to the terminal device. Theterminal device may determine, based on the correspondence between anMCS index and a base graph, the target base graph corresponding to thereceived target MCS index.

Table 1 is a schematic diagram of an MCS table.

TABLE 1 MCS Modulation Base Transport index order graph block size index0 2 1 0 1 2 2 0 2 2 1 1 3 2 2 1 4 4 1 2 5 4 2 2

A quantity of Raptor-like LDPC base graphs in the MCS table shown inTable 1 is 2. It is assumed that the base station may determine, basedon the CQI reported by the terminal device, to use the MCS index 0 andthe MCS index 1. This is because modulation orders and transport blocksizes corresponding to the two MCS indexes satisfy the CQI. If the basestation determines that the target base graph is the base graph 2, thebase station may send the MCS index 1 to the terminal device. Theterminal device may determine, based on the received MCS index, to usethe base graph 2 as the target base graph.

Optionally, in some other embodiments, the base station may send controlinformation to the terminal device, where the control informationincludes the indication information.

Optionally, in some embodiments, the control information may be downlinkcontrol information (DCI). The DCI may carry the indication informationexplicitly. For example, a field may be added to the DCI, and the fieldincludes at least one bit. The field may be used to carry the indicationinformation. The terminal device may determine the target base graphbased on the field. The DCI may alternatively carry the indicationinformation implicitly. For example, N fields respectively representingN Raptor-like LDPC base graphs may be defined. The base station mayperform an XOR operation on a field corresponding to the target basegraph and a specified field in the DCI. The terminal device may performthe XOR operation on the specified field and each of the N fields.Cyclic redundancy check on the DCI is likely to succeed only when theterminal device and the base station perform the XOR operation on samefields. The terminal device may determine a Raptor-like LDPC base graphcorresponding to a field that enables successful cyclic redundancy checkon the DCI, as the target LDPC base graph.

Optionally, in some embodiments, a code length of each to-be-encodedcode block may correspond to an lifting factor. A wireless transmissiondevice as a transmit end device may determine a target lifting factorbased on a code length of a to-be-encoded code block, and perform LDPCencoding on the code length of the to-be-encoded code block based on thetarget base graph and the target lifting factor. A wireless transmissiondevice as a receive end device may directly obtain the target liftingfactor from the transmit end device. The receive end device mayalternatively determine the target lifting factor based on the codelength of the to-be-encoded code block, and perform LDPC decoding onreceived information based on the target lifting factor and the targetbase graph. The code length of the to-be-encoded code block may be sentfrom the transmit end to the receive end device or may be determined bythe receive end device. A correspondence between the code length of theto-be-encoded code block and the lifting factor is stored in thewireless transmission device. In addition, it may be understood that, acorrespondence between a code length of a to-be-encoded code block andan lifting factor stored in the base station is the same as acorrespondence between a code length of a to-be-encoded code block andan lifting factor stored in the terminal device.

Optionally, in some other embodiments, a wireless transmission device asa transmit end device may determine a target lifting factor group in atleast two lifting factor groups based on requirement information, eachof the at least two lifting factor groups includes a plurality oflifting factors, and the requirement information includes at least oneof a terminal device type, a throughput rate requirement, a latencyrequirement, an initial-transmission code rate value, and a servicetype. The transmit end device may determine, based on a code length of ato-be-encoded code block, a target lifting factor in a plurality oflifting factors included in the target lifting factor group. Thetransmit end device may perform LDPC encoding on the to-be-encoded codeblock based on the target lifting factor and the target base graph.Similarly, a wireless transmission device as a receive end device mayalternatively determine a target lifting factor group in the at leasttwo lifting factor groups based on requirement information; determine,based on the code length of the to-be-encoded code block, the targetlifting factor in a plurality of lifting factors included in the targetlifting factor group; and perform LDPC decoding on a received code blockbased on the target lifting factor and the target base graph. It may beunderstood that, a rule of determining the target lifting factor by thetransmit end device is the same as a rule of determining the targetlifting factor by the receive end device, so that the receive end devicecan perform decoding correctly. In addition, the transmit end devicesends a length of a transport block to the receive end device. Thereceive end may determine the code length of the to-be-encoded codeblock according to a preset code block segmentation rule. The code blockreceived by the receive end device is obtained by the transmit enddevice by performing LDPC encoding on the to-be-encoded code block basedon the target lifting factor and the target base graph. The code blocksegmentation rule used by the receive end device is the same as a codeblock segmentation rule used by the transmit end device. Therefore, thecode length that is determined by the receive end device and that is ofthe to-be-encoded code block is the same as a code length that isdetermined by the transmit end device and that is of the to-be-encodedcode block.

Each of a plurality of lifting factors included in the at least twolifting factor groups may correspond to a code length of a to-be-encodedcode block. A code length of one to-be-encoded code block may correspondto different lifting factors in different lifting factor groups. Anlifting factor included in an lifting factor group is preset. The atleast two lifting factor groups and a correspondence between the codelength of the to-be-encoded code block and an lifting factor are storedin the wireless transmission device. It may be understood that, the basestation and the terminal device store same lifting factor groups and asame correspondence between a code length of a to-be-encoded code blockand an lifting factor.

A setting of lifting factor groups may correspond to the requirementinformation. It is assumed that there are two lifting factor groups. Afirst group of lifting factors in the two lifting factor groups isapplicable to encoding during which there is a relatively high latencyrequirement, and a second group of lifting factors is applicable toencoding during which there is a general latency requirement. In thiscase, if the transmit end device determines that there is a relativelyhigh latency requirement during encoding, the first group of liftingfactors may be determined as the target lifting factor group. Similarly,the lifting factor groups may be divided based on different servicetypes, terminal device types, throughput rate requirements,initial-transmission code rates, and the like. Certainly, differentlifting factor groups may alternatively correspond to differentrequirement information. For example, a group of lifting factors isapplicable to encoding during which there is a relatively high latencyrequirement, and another group of lifting factors is applicable toencoding during which there is a relatively high throughput raterequirement.

An initial-transmission code rate, also referred to as a first-timetransmission code rate and the like, is a transmission code rate forsending, after rate matching is performed on a code block havingundergone LDPC encoding, the encoded code block to the receive enddevice for the first time.

Based on the foregoing technical solution, the base station maydetermine a target base graph in a plurality of Raptor-like LDPC basegraphs that may be used to perform LDPC encoding, and indicate thetarget base graph to the terminal device. Further, for one code rate orone code length, the base station may select different base graphs asrequired. In addition, the plurality of Raptor-like LDPC base graphs mayalso support different code rates and different code lengths. This canincrease a range of supported code rates and code lengths.

FIG. 3 is a structural block diagram of a base station according to anembodiment of this application. As shown in FIG. 3, the base station 300includes a storage unit 301, a processing unit 302, and a sending unit303.

The storage unit 301 is configured to store N Raptor-like LDPC basegraphs.

The processing unit 302 is configured to determine a target base graphin the N Raptor-like LDPC base graphs stored in the storage unit 301, afirst base graph and a second base graph are any two of the NRaptor-like LDPC base graphs, a quantity of columns corresponding toinformation bits included in the first base graph is different from aquantity of columns corresponding to information bits included in thesecond base graph, an intersection between code lengths supported by thefirst base graph and the second base graph is not empty, an intersectionbetween code rates supported by the first base graph and the second basegraph is not empty, and N is a positive integer greater than or equal to2.

The sending unit 303 is configured to send indication information to aterminal device, where the indication information is used to indicatethe terminal device to use the target base graph to perform LDPCencoding and decoding.

The base station 300 shown in FIG. 3 may determine a target base graphin a plurality of Raptor-like LDPC base graphs that may be used toperform LDPC encoding and decoding, and indicate the target base graphto the terminal device. Further, for one code rate or one code length,the base station 300 may select different base graphs as required.

The storage unit 301 may be implemented by a memory, the processing unit302 may be implemented by a processor, and the sending unit 303 may beimplemented by a transmitter.

In addition, the base station 300 may further include a receiving unit,and the receiving unit may be configured to receive a code block sent bythe terminal device. The receiving unit may be implemented by areceiver.

For a specific function and a beneficial effect of each unit of the basestation 300, refer to the method shown in FIG. 2, and details are notdescribed herein again.

FIG. 4 is a structural block diagram of a terminal device according toan embodiment of this application. The terminal device 400 shown in FIG.4 includes a storage unit 401, a receiving unit 402, and a processingunit 403.

The storage unit 401 is configured to store N Raptor-like LDPC basegraphs.

The receiving unit 402 is configured to receive indication informationsent by a base station.

The processing unit 403 is configured to determine, according to theindication information, a target base graph used to perform LDPCencoding and decoding, where the target base graph is from the NRaptor-like LDPC base graphs stored in the storage unit 401, a firstbase graph and a second base graph are any two of the N Raptor-like LDPCbase graphs, a quantity of columns corresponding to information bitsincluded in the first base graph is different from a quantity of columnscorresponding to information bits included in the second base graph, anintersection between code lengths supported by the first base graph andthe second base graph is not empty, an intersection between code ratessupported by the first base graph and the second base graph is notempty, and N is a positive integer greater than or equal to 2.

The storage unit 401 may be implemented by a memory, the receiving unit402 may be implemented by a receiver, and the processing unit 403 may beimplemented by a processor.

For a specific function and a beneficial effect of each unit of theterminal device 400, refer to the method shown in FIG. 2, and detailsare not described herein again.

FIG. 5 is a structural block diagram of a base station according to anembodiment of this application. The base station 500 shown in FIG. 5includes a processor 501, a memory 502, and a transceiver circuit 503.

The components of the base station 500 are coupled together by using abus system 504. In addition to a data bus, the bus system 504 includes apower bus, a control bus, and a status signal bus. However, for clarityof description, various buses are denoted as the bus system 504 in FIG.5.

The method disclosed in the foregoing embodiment of this application maybe applied to the processor 501, or may be implemented by the processor501. The processor 501 may be an integrated circuit chip and has asignal processing capability. In an implementation process, the steps inthe foregoing method can be implemented by using a hardware integratedlogical circuit in the processor 501, or by using an instruction in aform of software. The foregoing processor 501 may be a general purposeprocessor, a digital signal processor (DSP), an application-specificintegrated circuit (ASIC), a field programmable gate array (FPGA) oranother programmable logic device, a discrete gate or transistor logicdevice, or a discrete hardware component. The processor 501 mayimplement or perform the methods, the steps, and logical block diagramsthat are disclosed in the embodiments of this application. The generalpurpose processor may be a microprocessor, or the processor may be anyconventional processor or the like. Steps of the methods disclosed inthe embodiments of this application may be directly performed andaccomplished by a hardware decoding processor, or may be performed andaccomplished by a combination of a hardware module and a software modulein the decoding processor. A software module may be located in a maturestorage medium in the art, such as a random access memory (RAM), a flashmemory, a read-only memory (ROM), a programmable read-only memory, anelectrically erasable programmable memory, or a register. The storagemedium is located in the memory 502. The processor 501 reads aninstruction in the memory 502 and completes the steps in the foregoingmethod in combination with the transceiver circuit 503.

FIG. 6 is a structural block diagram of a terminal device according toan embodiment of this application. The terminal device 600 shown in FIG.6 includes a processor 601, a memory 602, and a transceiver circuit 603.

The components of the terminal device 600 are coupled together by usinga bus system 604. In addition to a data bus, the bus system 604 includesa power bus, a control bus, and a status signal bus. However, forclarity of description, various buses are denoted as the bus system 604in FIG. 6.

The method disclosed in the foregoing embodiment of this application maybe applied to the processor 601, or may be implemented by the processor601. The processor 601 may be an integrated circuit chip and has asignal processing capability. In an implementation process, steps in theforegoing method can be implemented by using a hardware integratedlogical circuit in the processor 601, or by using an instruction in aform of software. The foregoing processor 601 may be a general purposeprocessor, a digital signal processor (DSP), an application-specificintegrated circuit (ASIC), a field programmable gate array (FPGA) oranother programmable logic device, a discrete gate or transistor logicdevice, or a discrete hardware component. The processor 601 mayimplement or perform the methods, the steps, and logical block diagramsthat are disclosed in the embodiments of this application. The generalpurpose processor may be a microprocessor, or the processor may be anyconventional processor or the like. Steps of the methods disclosed inthe embodiments of this application may be directly performed andaccomplished by a hardware decoding processor, or may be performed andaccomplished by a combination of a hardware module and a software modulein the decoding processor. A software module may be located in a maturestorage medium in the art, such as a random access memory (RAM), a flashmemory, a read-only memory (ROM), a programmable read-only memory, anelectrically erasable programmable memory, or a register. The storagemedium is located in the memory 602. The processor 601 reads aninstruction in the memory 602 and completes the steps in the foregoingmethod in combination with the transceiver circuit 603.

A person of ordinary skill in the art may be aware that, units andalgorithm steps in the examples described in the embodiments disclosedin this application may be implemented by electronic hardware or acombination of computer software and electronic hardware. Whether thefunctions are performed by hardware or software depends on a particularapplication and a designed constraint of the technical solutions. Aperson skilled in the art may use different methods to implement thedescribed functions for each particular application, but it should notbe considered that the implementation goes beyond the scope of thisapplication.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, reference may bemade to a corresponding process in the foregoing embodiments of method,and details are not described herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, a division of units ismerely a division based on a logical function, there may be other waysof division in actual implementation. For example, a plurality of unitsor components may be combined or integrated into another system, or somefeatures may be ignored or not be performed. In addition, the displayedor discussed mutual couplings or direct couplings or communicationconnections may be implemented through some interfaces. The indirectcouplings or communication connections between the apparatuses or unitsmay be implemented in electrical, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,that is, they may be located in one position, or may be distributed on aplurality of network units. Some or all of the units may be selectedbased on actual requirements to achieve the objectives of the solutionsof the embodiments.

In addition, functional units in the embodiments of this application maybe integrated into one processing unit, or each of the units may existalone physically, or two or more units are integrated into one unit.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, the embodiments may be implementedcompletely or partially in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instruction is loaded and executed on thecomputer, the procedure or the functions according to the embodiments ofthis application are all or partially generated. The computer may be ageneral-purpose computer, a special-purpose computer, a computernetwork, or another programmable apparatus. The computer instruction maybe stored in a computer-readable storage medium or may be transmittedfrom a computer-readable storage medium to another computer-readablestorage medium. For example, the computer instruction may be transmittedfrom a website, a computer, a server, or a data center to anotherwebsite, another computer, another server, or another data center in awired (for example, a coaxial cable, an optical fiber, or a digitalsubscriber line (DSL)) or wireless (for example, infrared, radio, andmicrowave, or the like) manner. The computer-readable storage medium maybe any usable medium accessible by a computer, or a data storage device,such as a server integrating one or more usable mediums, or a datacenter. The usable medium may be a magnetic medium (for example, afloppy disk, a hard disk, or a magnetic tape), an optical medium (forexample, a DVD), or a semiconductor medium (for example, a solid statedisk (SSD)), or the like.

The foregoing descriptions are merely specific implementations of thisapplication, but are not intended to limit the protection scope of thisapplication. Any variation or replacement readily figured out by aperson skilled in the art within the technical scope disclosed in thisapplication shall fall within the protection scope of this application.Therefore, the protection scope of this application shall be subject tothe protection scope of the claims.

What is claimed is:
 1. A method for data transmission, the methodcomprising: receiving, by a terminal device, indication information froma base station; and determining, by the terminal device according to theindication information, a target base graph used to perform low-densityparity-check (LDPC) encoding and decoding, wherein the target base graphis from N Raptor-like LDPC base graphs, a first base graph and a secondbase graph are any two of the N Raptor-like LDPC base graphs, a quantityof columns corresponding to information bits comprised in the first basegraph is different from a quantity of columns corresponding toinformation bits comprised in the second base graph, an intersectionbetween code lengths supported by the first base graph and code lengthssupported by the second base graph is not empty, an intersection betweencode rates supported by the first base graph and code rates supported bythe second base graph is not empty, and N is a positive integer greaterthan or equal to
 2. 2. The method according to claim 1, wherein theindication information is a modulation and coding scheme (MCS) index. 3.The method according to claim 2, wherein the determining, by theterminal device according to the indication information, the target basegraph comprises: determining, by the terminal device based on acorrespondence between an MCS index and a base graph, a base graphcorresponding to the MCS index as the target base graph.
 4. The methodaccording to claim 3, wherein the correspondence between the MCS indexand the base graph is indicated by an MCS table, wherein the MCS tablecomprises at least N MCS indexes, each of the at least N MCS indexescorresponds to one of the N Raptor-like LDPC base graphs, and each ofthe at least N MCS indexes further corresponds to at least one of amodulation order and a transport block size index.
 5. The methodaccording to claim 2, wherein the determining, by the terminal deviceaccording to the indication information, the target base graphcomprises: determining, by the terminal device, a transport block sizeand a modulation order according to the MCS index; determining, by theterminal device, a code length and a code rate according to thetransport block size and the modulation order; and determining, by theterminal device, the target base graph according to the code length andthe code rate.
 6. The method according to claim 1, further comprising:determining, by the terminal device based on a code length of ato-be-encoded code block, a target lifting factor; and performing, bythe terminal device, LDPC encoding on the to-be-encoded code block basedon the target lifting factor and the target base graph.
 7. The methodaccording to claim 1, further comprising: determining, by the terminaldevice based on a code length of a to-be-encoded code block, a targetlifting factor; and performing, by the terminal device, LDPC decoding onreceived information based on the target lifting factor and the targetbase graph.
 8. The method according to claim 1, wherein the indicationinformation is included in a control information.
 9. The methodaccording to claim 8, wherein the control information is downlinkcontrol information (DCI).
 10. An apparatus, comprising: a processor;and a non-transitory computer-readable storage medium coupled to theprocessor and storing programming instructions for execution by theprocessor, the programming instructions instruct the processor to:receive indication information from a base station; and determine,according to the indication information, a target base graph used toperform low-density parity-check (LDPC) encoding and decoding, whereinthe target base graph is from N Raptor-like LDPC base graphs stored inthe storage unit, a first base graph and a second base graph are any twoof the N Raptor-like LDPC base graphs, a quantity of columnscorresponding to information bits comprised in the first base graph isdifferent from a quantity of columns corresponding to information bitscomprised in the second base graph, an intersection between code lengthssupported by the first base graph and code lengths supported by thesecond base graph is not empty, an intersection between code ratessupported by the first base graph and code rates supported by the secondbase graph is not empty, and N is a positive integer greater than orequal to
 2. 11. The apparatus according to claim 10, wherein theindication information is a modulation and coding scheme (MCS) index.12. The apparatus according to claim 11, wherein the programminginstructions instruct the processor to: determine, based on acorrespondence between an MCS index and a base graph, a base graphcorresponding to the target MCS index as the target base graph.
 13. Theapparatus according to claim 12, wherein the correspondence between anMCS index and a base graph is indicated by an MCS table, wherein the MCStable comprises at least N MCS indexes, each of the at least N MCSindexes corresponds to one of the N Raptor-like LDPC base graphs, andeach of the at least N MCS indexes further corresponds to at least oneof a modulation order and a transport block size index.
 14. Theapparatus according to claim 11, wherein the programming instructionsinstruct the processor to: determine a transport block size and amodulation order according to the MCS index; determine a code length anda code rate according to the transport block size and the modulationorder; and determine the target base graph according to the code lengthand the code rate.
 15. The apparatus according to claim 10, wherein theprogramming instructions instruct the processor to: determine, based ona code length of a to-be-encoded code block, a target lifting factor ina plurality of lifting factors comprised in the target lifting factorgroup; and perform LDPC encoding on the to-be-encoded code block basedon the target lifting factor and the target base graph.
 16. Theapparatus according to claim 10, wherein the programming instructionsinstruct the processor to: determine, based on a code length of ato-be-encoded code block, a target lifting factor in a plurality oflifting factors comprised in the target lifting factor group; andperform LDPC decoding on received information based on the targetlifting factor and the target base graph.
 17. The apparatus according toclaim 10, wherein the indication information is included in a controlinformation.
 18. The apparatus according to claim 17, wherein thecontrol information is downlink control information (DCI).
 19. Anon-transitory computer readable medium comprising computer programcodes stored thereon, wherein the program codes are executable by one ormore digital processors to cause a computing device to perform steps of:receiving indication information from a base station; and determiningaccording to the indication information, a target base graph used toperform low-density parity-check (LDPC) encoding and decoding, whereinthe target base graph is from N Raptor-like LDPC base graphs, a firstbase graph and a second base graph are any two of the N Raptor-like LDPCbase graphs, a quantity of columns corresponding to information bitscomprised in the first base graph is different from a quantity ofcolumns corresponding to information bits comprised in the second basegraph, an intersection between code lengths supported by the first basegraph and code lengths supported by the second base graph is not empty,an intersection between code rates supported by the first base graph andcode rates supported by the second base graph is not empty, and N is apositive integer greater than or equal to
 2. 20. The non-transitorycomputer readable medium according to claim 19, wherein the indicationinformation is a modulation and coding scheme (MCS) index.
 21. Thenon-transitory computer readable medium according to claim 20, whereindetermining the target base graph comprises: determining, based on acorrespondence between an MCS index and a base graph, a base graphcorresponding to the MCS index as the target base graph.
 22. Thenon-transitory computer readable medium according to claim 21, whereinthe correspondence between an MCS index and a base graph is indicated byan MCS table, wherein the MCS table comprises at least N MCS indexes,each of the at least N MCS indexes corresponds to one of the NRaptor-like LDPC base graphs, and each of the at least N MCS indexesfurther corresponds to at least one of a modulation order and atransport block size index.
 23. The non-transitory computer readablemedium according to claim 20, wherein determining the target base graphcomprises: determining a transport block size and a modulation orderaccording to the MCS index; determining a code length and a code rateaccording to the transport block size and the modulation order; anddetermining the target base graph according to the code length and thecode rate.
 24. The non-transitory computer readable medium according toclaim 19, wherein the program codes executable by one or more digitalprocessors further cause the computing device to perform steps of:determining, based on a code length of a to-be-encoded code block, atarget lifting factor; and performing LDPC encoding on the to-be-encodedcode block based on the target lifting factor and the target base graph.25. The non-transitory computer readable medium according to claim 19,wherein the program codes executable by one or more digital processorsfurther cause the computing device to perform steps of: determining,based on a code length of a to-be-encoded code block, a target liftingfactor; and performing LDPC decoding on received information based onthe target lifting factor and the target base graph.
 26. Thenon-transitory computer readable medium according to claim 19, whereinthe indication information is included in a control information.
 27. Thenon-transitory computer readable medium according to claim 26, whereinthe control information is downlink control information (DCI).